This invention relates to apparatus for use in container erection installations, for handling partly completed containers in the form of skillets, and to methods of handling partly formed containers.
Polygonal containers, e.g. made from paper or board, are commonly made by cutting blanks from the sheet material, with impressed fold lines. The blanks are erected by folding the main body to form a polygonal tube which is closed by a glued seam along one longitudinal edge. This tubular form of blank is known as a skillet. Subsequently, integral flaps and tabs at both ends of the blank are folded over and glued as necessary to close the ends of the container. Before the container is fully closed, it may be filled with its intended contents.
If the containers are to be machine-filled, they may be supplied partly formed to the filling installation, as flattened tubular blanks or skillets. For example, EP 461084A describes an apparatus in which flattened tubular blanks or skillets are drawn from a reservoir stack by a swinging arm to be placed on a conveyor belt. The skillets are partly opened by a stationary guide as they move between reservoir and container and in order to place them at the required locations the conveyor belt is stationary during the transfer movement. When the conveyor belt is restarted temporary holding means shapes the tubular form further. The skillet achieves its final rectangular tubular form only when it reaches a second conveyor belt opposite the first belt, as it is brought between locating means on both belts.
DE 3010891 describes another skillet supply arrangement in which a swinging arm moves the skillets from reservoir stack to a conveyor. A suction device is articulated on the arm and moves onto the skillet drawn from the stack to begin to open the skillet as it moves towards the conveyor. In order to do this it is required to pivot on the arm about a centre some distance from the skillet and a large angular movement of the device will therefore either distort the skillet or will result in device slipping and its suction grip being lost. The arrangement described in fact also proposes the use of a stationary guide to complete the opening of the skillets, which makes a large angular movement of the suction device unnecessary.
Both these known arrangements have the further disadvantage that the skillet stack protrudes transversely to the conveyor path. This can increase the overall space requirements of the installation comprising the reservoir stack and conveyor. In both instances, furthermore, the swinging arm is brought between the conveyor and the skillet as it deposits the opened skillet in the conveyor. There must therefore be a pause while the conveyor moves the deposited skillet onwards before the arm can return to the stack. The need to provide clearance for the arm between the skillet and the conveyor may also impose constraints on the design of the conveyor.